1. Field
This disclosure relates to an electrolyte for a rechargeable lithium battery and a rechargeable lithium battery including the same.
2. Description of the Related Technology
Lithium rechargeable batteries using an organic electrolyte solution have twice or more the discharge voltage than a conventional battery using an alkali aqueous solution, and accordingly have high energy density.
Composite oxides such as LiCoO2, LiMn2O4, LiNiO2, LiNi1−xCoxO2 (0<x<1), LiMnO2, and the like have been studied as positive active materials for rechargeable lithium batteries. The negative active materials of rechargeable lithium batteries have been made of various carbon-based materials such as artificial and natural graphite, hard carbon, which can all intercalate and deintercalate lithium ions.
One or more lithium salts dissolved in a carbonate-based solvent has been generally used as an electrolyte for rechargeable lithium batteries. Recently, in order to improve flame retardancy of an electrolyte solution, an addition of phosphoric acid-based retardant to a mixture of cyclic and linear carbonate solvents has been suggested.
However, the phosphoric acid-based retardant causes severe reductive decomposition in an interface between a negative electrode and the electrolyte solution to decrease available capacity of the negative electrode and increase cell resistance. Thereby, it suppresses a smooth intercalation reaction of lithium ions.
Furthermore, if the phosphoric acid-based retardant is added in an excessive amount in a solvent level instead of in an additive level, the cycle-life characteristics of a battery produced therewith is significantly decreased.